Is the Freemarker Plugin source available?

I'm planning to hack away the Non-Dairy Soy plugin (Clojure) and wanted an example plugin to read and understand the code.I'm keen to implement auto-completion especially.

We use the Freemarker plugin quite a bit so was thinking that it might be a good place to start. Does anyone know if the source is available? Or even better, places to look at a source for doing variable copletion?

I've seen http://confluence.jetbrains.net/display/IDEADEV/Developing+Custom+Language+Plugins+for+IntelliJ+IDEA and that's about it

Cheers,

Mark C